TypeError: Error when calling the metaclass bases

[Jaroslav Guenther]

Hello,

I am getting:

[...]
File "/usr/lib/python2.7/site-packages/jwkest/extra.py", line 3, in
from jwkest.jws import JWSException
File "/usr/lib/python2.7/site-packages/jwkest/jws.py", line 116, in
class HMACSigner(Signer):
TypeError: Error when calling the metaclass bases
str() takes at most 1 argument (3 given)
when trying to do sphynx build of my code
https://travis-ci.org/rucio/rucio/jobs/617413102?utm_medium=notification&utm_source=github_status

I have seen here troubles with metaclasses, could this issue be related, how could I avoid this crash ?
https://github.com/IdentityPython/pyjwkest/tree/master/src/jwkest

[Jaroslav Guenther]

When Sphinx loaded the external modules for my program, it got stuck 
when it tried to execute a globally called function. I replaced these modules by Mock classes so that they are not being parsed by Sphinx and prevented the function to call these modules at the time the doc is being built.